In most email systems there are two states for an email in the inbox; unopened (unread) or opened (read). However, these two binary states do not provide any nuance about such issues as the degree to which an email has actually been read or scrutinized. For instance, if a new email is opened (or previewed) quickly, the user may have only obtained a vague notion of subject, content, other people involved, etc., yet the email will be shown to have been opened. This can mislead the user, for example, by causing them to believe that the email has been reviewed when the user reopens his or her inbox at a later time.
Furthermore, users of conventional email systems have access to very little information about an email they have sent to one or more users after the email is sent. Using “read receipts,” the recipient of such an email can send a notification to the sender notifying them that they have opened the email. However, such a read receipt suffers from similar problems as those discussed above regarding binary email states, namely that the sender lacks information about the degree to which the sent email has been reviewed.